Radio loud speaker



July 7, 1931. c. H. DUFFY RADIO LOUD SPEAKER Filed April 25, 1930 3% WM W Patented July 7, 1931 UNITED STATES CHARLES HUGH DUFFY, OF MIAMI, FLORIDA RADIO LOUD SPEAKER Application filed April 25, 1930.

Serial No. 447,390.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 20, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to sound reproducers but more particularly to diaphragms for radio loud speakers and the like.

The invention has for its object to improve the tonal qualities of the reproduced sound,

first by improving the shape and arrangement of the diaphragm, and secondly, by the use of a diaphragm material such as celluloid.

In diaphragms of the general type to which this invention relates, in which the diaphragm material is flexed in a roll or rolls into one or more substantially semi-circular forms, the rear portions of the diaphragm form partial- 1y enclosed recesses which have the tendency to create an objectionable resonance.

It is one of the purposes of this invention to correct such condition by flexing the diaphragm material in substantially quarter circle formations, so that the planes of the outer edges of the diaphragm are substantially at right angles to the planes of the central meeting edges of the diaphragm.

I have found that such a form of diaphragm lends itself more perfectly to cabinet installation than the semi-circular form, in that it permits the outer edges of the diaphragm to lie in the same plane with and directly behind and against the front of the cabinet, which front then forms an. eflicient baffle for the side edges of the diaphragm.

I have also found that such a form of diaphragm lends itself to be effectively baffled at its top and bottom edges, as will hereinafter more fully appear.

I am aware that celluloid has been used for small flat telephone receiver and phonograph reproducers or the like, but I lay no claim to flat or conical shaped diaphragms, or to any diaphragms whatsoever, in which the celluloid is not flexed in roll formation.

I have found that celluloid when used in such roll formation presents a maximum amount of elasticity at the central meeting edges, and that by reason of such maximum elasticity, the central meeting edges of the diaphragm follow the pulsations of the actuating unit or units and respond to such pulsations more perfectly than does any other material with which I am familiar.

I have also found that while such maximum amount of elasticity is present in such flexed celluloid diaphragm formation, this material by reason of its dense and homogeneous nature appears to resist the tendency to ripple or take on parasitic vibrations.

In consequence of all of these characteristics. the efficiency of such a diaphragm is high. There is an absence of objectionable or unnatural resonance, while the tonal quality of the reproduced sound is pure and natural.

Referring to the accompanying drawings:

Fig. 1 is a diagrammatic view of the diaphragm in top plan.

Fig. 2 is a front elevation illustrating the diaphragm in a cabinet installation.

Fig. 3 is a horizontal sectional view taken on line 33 of Fig. 2, and

Fig. 4 is a vertical sectional view taken on line 44l of Fig. 2.

Like numerals of reference indicate the same parts throughout the several figures, in which :-l indicates the diaphragm, and 2 indicates a cabinet of any design, the same having a front 3, and sides 4. The front 3 has an opening 5, behind which the diaphragm 1 is mounted.

The diaphragm 1 is preferably constructed of two sheets of celluloid or material having like characteristics, though not necessarily limited thereto, having their central meeting edges 6 spaced apart by a strip 7 of sound damping material such as felt. This strip 7 separates the adjacent edges of the two celluloid sheets so that they do not touch each other and vibrate independently of each other.

In the preferred embodiment of this invention, the length of the diaphragm is in 6X- cess of the width, and the two meeting edges 6 are preferably of the same or substantially any suitable manner to the meeting edges 6 of the diaphragm 1.

Each sheet of the diaphragm is flexed into substantially a quarter circle as shown in Fig. 1, and the outer edges are inserted under the clamping strips 9 which are tightly screwed down upon the edges of the diaphragm.

Before placing the diaphragm in this position, and before flexing the sheets, I apply to the top and bottom edges of the diaphragm a strip of soft dense but pliable material 9' such as chamois skin, so that this material projects slightly beyond the top and bottom edges of the diaphragm. The diaphragm with these applied strips thereon is then flexed and clamped in place as just described. The extending portions of the chamois skin are then laid fiat against the adjacent horizontal partitions l0 and are secured in such position by pieces 11 of thin stiff material by suitable fastenings 12. These strips of soft pliable material which are applied, as by cement, to the top and bottom edges of the diaphragm and are also fastened flat against the adjacent horizontal partitions 10 of the cabinet provide a substantially air-tight but flexible connection between the diaphragm and the adjacent horizontal partitions 10 and effectively prevent the vibratory waves from passing from the front of the diaphragm t0 the rear of the diaphragm to create aninterference harmful to the audibility of the low frequency vibrations, and thus cause the cabinet to act as a bafiie. WVhile these soft, dense and pliable strips function in'that manner, they at the same time do not restrain the free and elastic movement of the diaphragm under the influence of the actuating unit or units.

Having thus described one embodiment of the invention, I do not wish to be understood as limiting myself to the specific construction shown and described, but consider myself clearly entitled to all such changes and modifications as fall within the limit and scope of the appended claims:

lVhat I claim as new and desire to secure by Letters Patent of the United States is 1. A diaphragm for radio speakers and the like comprising two sheets of celluloid flexed into two substantially quarter circle formations so that the plane of the side edges of the sheets lies at substantially right angles to the plane of the meeting edges of the sheets, means for clamping the said side edges of the sheets of the diaphragm, strips of soft pliable material applied to the top and bot-tom edges of the diaphragm, means adjacent the said edges to receive said strips to prevent the vibratory waves from passing from front to back of the diaphragm at the top and bottom edges thereof and means for fastening the said soft pliable strips to the said means adjacent the said edges.

2. A diaphragm for radio speakers and the like, composed of sheet celluloid flexed into two substantially quarter circle formations, so that the plane of the side edges of the sheets lies at substantially right angles to the plane of the meeting edges of the sheets,

,the said meeting edges and the said side the like, composed of sheet celluloid flexed;

into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to the plane of the meeting edges of the two quarter circle formations, the said meeting edges and thesaid side edges being substantially the same length, means for clamping the side edges of the diaphragm, and means at the top and bottom edges of the diaphragm for preventing the vibratory waves from passing from front to back of the diaphragm over the top and bottom edges thereof.

i. A diaphragm for radio speakers and the like composed of sheet celluloid flexed into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to the plane of the meeting edges of the two quarter circle formations, the said meeting edges and the said side edges being substantially the same'length, and means at the top and bottom edges of the diaphragm for preventing the Vibratory waves from passing from front to back of the diaphragm over the top and bottom edges thereof.

5. A diaphragm for radio speakers and the like composed of sheet celluloid flexed into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to the planerof the meeting edges of the two quarter circle formations, the said meeting edgesand the said side edges being substantially the same length and baffling means extending from the said side edges parallel with the plane thereof.

6. A diaphragm for radio speakers and the like composed of sheet celluloid flexed into two roll formations, means for clamping the side edges of the diaphragm, and means at the top and bottom edges of the diaphragm for preventing the vibratory waves from passing from front to back of the diaphragm atthe top and bottom edges thereof, the latter means including horizontal members adjacent the top and bottom edges of the diaphragm, and including strips of soft pliable material applied to the top and bottom edges of the diaphragm, and including means for securing said strips of soft pliable material to the horizontal members to provide substantially air-tight connections between ghe diaphragm and the said horizontal memers.

' 7. A diaphragm for radio speakers and the like composed of sheet celluloid flexed into two roll formations, and means at the top and bottom edges of the diaphragm for preventing the vibratory waves from passing from front to back of the diaphragm at the top and bottom edges thereof.

8. A diaphragm for radio speakers and the like composed of sheet material flexed into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to the plane of the meeting edges of the two quarter circle formations, means for clamping the side edges of the diaphragm, strips of soft pliable material applied to the top and bottom edges of the diaphragm, means adjacent the latter edges to receive said strips to prevent the vibratory waves from passing from front to back of the diaphragm at the top and bottom edges thereof and means for fastening the strips of soft pliable material to the means adjacent the top and bottom edges of the diaphragm to provide substantially air-tight connections between the diaphragm and the said means adjacent the top and bottom edges thereof.

9. A diaphragm for radio speakers and the like composed of sheet material flexed into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to Y the plane of the meeting edges of the two quarter circle formations, the meeting edges and the side edges being substantially the same length, means for clamping the side edges of the diaphragm and means applied to the top and bottom edges of the diaphragm to prevent the vibratory waves from passing from front to back of the diaphragm at the top and bottom edges thereof, and means extending over the top edge and under the bottom edge of the diaphragm to fixedly receive the means applied to the top and bottom edges of the diaphragm to provide substantially air-tight connections at the top and bottom edges of the diaphagm.

10. A diaphragm for radio speakers and the like, composed of sheet material flexed into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to the plane of the meeting edges of the two substantially quarter circle formations, the meeting edges and the side edges being substan tially the same length, means for clamping the side edges of the diaphragm, and means at the top and bottom edges of the diaphragm for preventing the vibratory waves from passing from front to back of the diaphragm over the top and bottom edges thereof, the latter means including a member extending over the top edge and under the bottom edge of the diaphragm and soft pliable strips fixedly connected to the top edge of the dia phragm and to its adjacent extending member and fixedly connected to the bottom edge of the diaphragm and to its adjacent extending member.

11. A diaphragm for radio speakers and the like composed of sheet material flexed into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to the plane of the meeting edges of the two quarter circle formations, the length of the meeting edges and the side edges being sub stantially the same, and means at the top and bottom edges of the diaphragm for preventing the vibratory waves from passing from front to back of the diaphragm over the top and bottom edges thereof, said means including soft pliable pieces fixedly attached to the top and bottom edges of the diaphragm and members extending adjacent to the top and bottom edges to fixedly receive said soft pliable pieces.

12. A diaphragm for radio speakers and the like composed of sheet material flexed into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to the plane of the meeting edges of the two quarter circle formations and a strip of soft sound damping material interposed between the meeting edges of the diaphragm.

1.3. A diaphragm for radio speakers and the like composed of sheet material flexed into two roll formations, means for clamping the side edges of the diaphragm, and means at the top and bottom edges of the diaphragm for preventing the vibratory waves from pa ssing from front to back of the diaphragm at the top and bottom edges thereof and a strip of soft sound damping material interposed between the meeting edges of the diaphragm.

14. A diaphragm for radio speakers and the like composed of sheet material flexed into two roll formations, and means at the top and bottom edges of the diaphragm for preventing the vibratory waves from passing from front to back of the diaphragm at the top and bottom edges thereof and a strip of soft sound damping material interposed between the meeting edges of the diaphragm.

15. A diaphragm for radio speakers and the like comprising two sheets of celluloid flexed into two substantially quarter circle formations so that the plane of the side edges of the" sheets lies at substantially right angles to the plane of the meeting edges of the sheets, the length of the diaphragm being greater than the \JlCltll, a strip of soft sound damping material interposed between the meeting edges of the diaphragm, means for clamping the said side edges of the sheets of the diaphragm, sound baffling means extending from the side edges parallel to the plane of the side edges, strips of soft pliable material applied to the top and bottom edges of the diaphragm, members extending over the trap and under the bottom of the diaphragm a jacent the top and bottom edges thereof, and means for securing the strips of soft pliable material to the said members to provide substantially airtight connections between the diaphragm and the said members to prevent the vibratory Waves from passing from front to back of the diaphragm at the top and bottom edges thereof.

16. A diaphragm for radio speakers and the like comprising two sheets of celluloid flexed into roll formation, the length of the diaphragm being greater than the width, a strip of sound damping material interposed between the meeting edges of the diaphragm, means for clamping the diaphragm in roll formation, strips of soft pliable material applied to the top and bottom edges of the diaphragm, members extending over the top and under the bottom of the diaphragm and adjacent the top and bottom edges thereof, and means for securing the strips of soft pliable material to the said members to provide substantially air-tight connections between the diaphragm and the said members to prevent the vibratory waves from passing from front to back of the diaphragm at the top and bottom edges thereof.

17. A diaphragm for radio speakers and the like comprising two sheets of sheet material flexed into two substantially quarter circle formations so that the plane of the side edges of the sheets lies a; substantially right angles to the plane of the meeting edges of V the sheets, the length of the diaphragm being greater than the Width and the length of the meeting edges and the side edges being substantially the same, astrip of soft sound damping material interposed between the meeting edges of the diaphragm, means for clamping the side edges of the sheets of the diaphragm, sound baffling means extending from the side edges of the diaphragm parallel to the plane of the side edges of the diaphragm, strips of soft pliable material applied to the top and bottom edges of the diaphragm, members extending over the top and under the bottom of the diaphragm adjacent to the top and bottom edges thereof, and means for securing the strips of soft pliable material to the said members to provide substantially air-tight connections between the diaphragm and the said members to prevent the vibrating waves from passing from front to back of the diaphragm at the top and bottom edges thereof.

1.8. A diaphragm for radio speakers and the like composed of sheet celluloid flexed into two substantially 'uarter circle form!- tions so that the plane 0 the side edges of the diaphragm lies at substantially right angles to the planeof the meeting edges of the two quarter circle formations, a strip of sound damping material interposed between the meeting edges of the two quarter circle formations, and sound baffling means extending from the side edges of the diaphragm.

19. A diaphragm for radio speakers and the like composed of sheet celluloid flexed into two substantially quarter circle formations so that the plane of the side edges of the diaphragm lies at substantially right angles to the plane of the meeting edges of the two loo 

